Dehumidifier - Runs constantly, but I would have expected it to produce more water..

[nyorksjc]

I recently moved into a new house, and inherited a four year old Haier AHD40, 40 pint dehumidifier which runs in an unfinished basement. Now that the summer is here, the thing is running around the clock, keeping the humidity in the basement at around 65%. I live in Connecticut, where electricity prices are around 20 cents per k/wh.

I have tested the unit to see how much electricity it is using, and it turned out to be around 16 kw/h over 24 hours, which, when I do the Math, is going to set me back around $90 a month. Ouch!

The thing is, that for my 16 kw/h of electricity, the unit managed to suck up just over 7 liters of water, which works out to be less that a half a liter of water for every kw/h it uses. I was reading on the energy star website, that modern dehumidifiers should be able to suck up about 1.5 liters of water per kw/h used.

I am wondering that if I were to replace the unit for a new one, would I get better efficiency. It would add insult to injury if I were to shell out a couple of hundred dollars for a new unit, and still be paying $90 to run thru the summer months.

Any thoughts from anyone would be greatly appreciated...

[willshak]

on 8/13/2007 6:41 PM [e-mail] said the following:

It's an unfinished basement. Paint the walls with a moisture barrier paint and the dehumidifier will run less. The cost of the paint would be less than a month's worth of electricity.

[Clark]

I'm using two dehumidifiers willshark, that paint thing sounds like a good idea!

Clark

[nyorksjc]

Thanks Bill. I will probably do the painting as well, but I was wondering if the dehumidifier wasn't working correctly due to the the fact that it is removing less that half a liter of water per kw/h. If it is under performing, it would make sense to replace the unit, but I would be loathe to do that if a newer unit performed no better.

[willshak]

I don't know where you are, but here in NY, I finished off the basement with studded, insulated, vapor barriered, sheetrocked walls and my single dehumidifier hardly runs at all.

[dpb]

[nicksanspam]

And adding heat to the house.

... 16 kWh (note units) is 54.6K Btu.

Condensing 7 liters of water adds an additional 15.4K Btu.

You might circulate basement air up through the house whenever the basement RH is greater than 60%, using a humidistat (maybe the one in the Haier unit) and use an $80 window AC upstairs to remove moisture and cool vs warm the house in summertime.

Where is the moisture coming from?

Nick

[nyorksjc]

As far as I can tell the moisture is coming from the the normal humidity in the air, that you would get in the hot summer months. There is an additional crawl space with a dirt floor, which I am also sure adds to the amount of moisture in the basement. However, we moved into the house at the end of April. I know that in May the dehumidifier was only running part of the time, so the summer is the main reason for the increased humidity.

Your idea about circulating the air up through the house might be worth thinking about, but what I am really wondering is if the dehumidifier, at just four years old, should be removing more that 7 liters of water for 16 kwh of electricity, as the energy star website suggests that a modern dehumidifier should be able to remove 1.5 liters per kwh. If I were to buy a new unit which started to remove the moisture at 1.5 liters kwh, then this would surely have the effect of reducing the humidity in the basement to less than 60% far quicker than my unit, which would mean that it wasn't running all the time, and would instantly slash my power bill.

I am wondering if anyone knows why a dehumidifier, that is rated to remove 1.5 liters of water per kwh, would fail to do just that? Is the only reason because the unit was faulty, or are there environmental factors?

[fire]

I had a dehumidifier do EXACTLY what you are describing. Ran constantly and didn't seem to be doing much. I discovered that the fins were blanketed by a layer of dust. I cleaned the fins and all is fine. It now removes a ton of water and runs far less. It made a huge impact on my electric bill as well. Dropped roughly $80 a month!

[nicksanspam]

Sounds like airsealing would help.

And plastic over the dirt floor.

Sounds like it should be.

And what's this Munters DC120 that removes 3.3 liters/kWh? Googling produces nothing but the energy star list...

Nick

[Chris Lewis]

According to :

It doesn't sound that old, so, it should be doing better than that.

It may be that it just needs a thorough cleaning of the coils and fins. If there's lots of dust on it, it will act as an insulator, and greatly reduce efficiency. May need to resort to an air compressor and/or fine & soft brushes.

In a basement, it may have picked up rather a lot of dust in a few years if they did any renovation (eg: drywall sanding ;-).

Note also that if you're not getting the water right out of the basement (eg: run the outflow directly into a drain), you'll be losing some effectiveness through re-evaporation. Sorta like having both the cold and hot side of an A/C in the same room - the net result is the room doesn't get cooler...

[nyorksjc]

You may be onto something... I have just taken a closer look at the unit and there is a plastic mesh filter which covers the space at the rear of the unit, and therefore encloses the fins. Until the closer inspection, I did not even realize that it was even a filter, due to the build up of filth and dirt on the mesh. I just thought it was a dirty cover. I have removed the mesh cover, temporarily, and will see what happens over the next twenty four hours... I will be delighted if this solves the mystery, as I just could not believe how much the thing was costing to run. Thanks a million.

[fire]

You will probably need to remove the front cover as well, and clean there. If air can't circulate past the fins, the unit will run endlessly without doing any dehumidifying. Mine had more dirt and dust clogging the front than the rear. I had to partially disassemble the unit to gain access to all that needed cleaning. I ended up taking it outside and using a garden hose.

[nyorksjc]

Since I took the back cover off, the unit has actually clicked off!!! A wonderful feat in itself, and it also brought down the humidity to less that 60% for about the first time ever. By my calculations, it is using 30-40% less electricity already, but I intend to clean as much of the other components that I can, and hopefully, that may improve things even further. Thanks again for going to the trouble of replying to this mail.

[fire]

I'm glad it seems to be working out for you.

[Chris Lewis]

According to :

Pay special attention to cleaning the cooling fins. Even with a filter, if it hasn't been cleaned out in years, there's bound to be a lot of dust on the fins. That alone will decrease efficiency by quite a bit.